The invention concerns an extrusion device for impregnating a rock formation, preferably for bonding with a liquid synthetic product, with the use of a piston pump having at least one working cylinder.
The invention is applicable, in particular, to underground excavation operations and to the impregnation of the rock or the mineral, respectively, in particular, overhanging coal. Preferably, the invention is used for stabilizing the formation by bonding teary strata with the aid of a diisocyanate and polyalcohol by using polyurethane foam compound consisting of these two components. Although the invention can, be applied for saturating the face of the coal with water, it is explained in detail in the following description of its application to the extrusion of the so-called standard compound for mining of the two component foam compounds mentioned above.
For this application of the invention a working cylinder must be provided for each of the two components, because the two liquid components may only be combined in a bore hole. For this type of piston pump a working cylinder may be provided. Occasionally it is practicable to align a driving cylinder with each working cylinder so as to apply the propulsive force more advantageously to the driving piston. On the one hand, the control of the driving cylinder must insure that the driving pistons are operated with the force required to operate the working piston. On the other hand, the control must insure a timely reversal at the end of each cycle and that the energy contained in the working fluid is converted most effectively into pump energy.
According to the prior published state of the art (magazine Gluckauf 113 (1977), 707, 711), a gear pump is driven by a pneumatic motor. It has the disadvantage that compressed air is not always available in the needed amount and at favorable energy cost and, further, the gear pump must be able to handle component extrusion fluids of different viscosities, as is the rule with the above mentioned standard compound for mining. Differences in viscosity between the two extrusion fluids makes adherence to the specified ratio of the liquid components practically impossible, primarily because of the unavoidable loss by leakage, thereby resulting in reduced efficiency.